The invention relates to a circuit arrangement for operating an energy storage system of an electric and/or hybrid vehicle, as well as to an energy storage system.
In automotive engineering, it is known to use high-voltage batteries that provide the current needed to drive an electric motor in an electric and/or hybrid vehicle. In motorized operation of the electric and/or hybrid vehicle, electric energy can be transferred from the so-called traction battery to the electric motor via a so-called traction network. In a generator operation (recuperation operation), the electric energy can be transferred from the electric motor to the traction battery via the traction network. For safety reasons, the traction battery must be electrically separable from the traction network and from electric or electronic elements composing the traction network. For this purpose, there generally are so-called breakers or circuit breakers arranged between connection points of the traction battery and connection points of the traction network.
The present invention addresses the problem of providing a circuit arrangement for operating an energy storage system of an electric and/or hybrid vehicle, and an energy storage system, which enable a sufficiently reliable electric isolation of an energy store from an electric energy network of an electric and/or hybrid vehicle.
The problem is solved according to a first aspect of the invention by a circuit arrangement for operating an energy storage system of an electric and/or hybrid vehicle. The circuit arrangement includes an analog monitoring circuit, which is designed and arranged to detect a measurement signal that is representative of a current flowing through the energy store, and to generate a predetermined first control signal in a manner dependent on the measurement signal. The circuit arrangement further includes a semiconductor switching element which is designed to electrically couple, in a first switching state, the energy store to an electrical energy network, and, in a second switching state, to electrically decouple the energy store from the electrical energy network, wherein the semiconductor switching element comprises a control terminal which is coupled by signaling technology to an output of the monitoring circuit, and the switching state of the semiconductor switching element is adjustable in a manner dependent on the first control signal.
Advantageously, this makes it possible to limit, to a predetermined value, a maximum current flowing through the energy store. This is particularly advantageous in that a warranty limit and, accordingly, a manufacture specification for the maximum current flowing through the energy store and, in particular, through cells of the energy store is not exceeded. Warranty costs can thereby be reduced, and a contribution can be made to reducing environmental pollution, because the respective energy store can have a longer life. The satisfaction of a user of the vehicle can also be enhanced, because the likelihood that the energy store must be replaced due to the exceeding of the maximum current can be kept low. The decoupling of the energy store from the energy network can be done very quickly, because of an extremely short response time of the monitoring circuit, such that lines of the energy network can be laid for a lower short-circuit current and demands in terms of a short-circuit strength of the lines and/or connectors are reduced. This makes it possible to pare down further production costs for the electric and/or hybrid vehicle. Advantageously, the quick response time of the analog monitoring circuit makes it possible to detect the short-circuit and/or overcurrent so quickly, and isolate the energy store from the energy network so quickly, that an additional protective fuse can be forgone. The semiconductor switching element is advantageous in that very little space is required and in that capacity that needs to be provided to control the semiconductor switching element can be kept very low.
The energy network may include a load, and in particular an electric motor for driving the electric and/or hybrid vehicle with associated power electronics. The circuit arrangement may preferably have one or two semiconductor switching elements, whereby a unipolar or bipolar isolation of the energy store from the energy network is possible. Preferably, the energy store is a high-voltage energy store. A high-voltage energy store designates here an energy store that operates a drive train. In an advantageous embodiment of the first aspect, the circuit arrangement includes a digital control device. The digital control device is designed to generate a predetermined second control signal in a manner dependent on at least one predetermined energy store-related operational quantity, at least one predetermined vehicle-related environmental quantity, at least one predetermined vehicle-related operational quantity, and/or at least one predetermined energy network-related operational quantity. The second control signal is output at a predetermined interface that is coupled by signaling technology to the control terminal of the semiconductor switching element. The switching state of the semiconductor switching element is adjustable in a manner dependent on the second control signal. This is advantageous in that the energy store can be isolated from the energy network or electrically coupled to the energy network in a manner dependent on other quantities.
In another advantageous embodiment, a predetermined course of the first control signal is representative of a request for the semiconductor switching element to occupy the second switching state. Additionally, a predetermined course of the second control signal is representative of a request for the semiconductor switching element to occupy the second switching state. If the first control signal or the second control signal—or both control signals—has the respective predetermined course, then the control terminal of the semiconductor switching element is controlled such that the semiconductor switching element occupies the second switching state. This is advantageous in that regardless of whether a short-circuit and/or overcurrent is detected from the analog monitoring circuit or from the control device, the energy store is isolated from the energy network. This independence may be advantageously used for the functional safety in the vehicle.
In another advantageous embodiment of the first aspect, a predetermined further course of the second control signal is representative of a request for the semiconductor switching element to occupy the first switching state. If the second control signal includes the predetermined further course and the first control signal does not comprise the predetermined course, then the control terminal of the semiconductor switching element is controlled such that the semiconductor switching element occupies the first switching state. This is advantageous in that if a short-circuit current or overcurrent is not detected, then the energy store can be electrically coupled to the energy network in a manner dependent on the additional quantities.
In a further advantageous embodiment according to the first aspect, the semiconductor switching element has at least one field effect transistor. Advantageously, the field effect transistors that are designed so as to be suitable for such usage have a much higher switching speed than mechanical relays, protective circuits, or fuses, so that the energy store can be much more rapidly isolated from the energy network than with mechanical relays, protective circuits, or fuses.
In another advantageous embodiment according to the first aspect, the semiconductor switching element includes at least one field effect transistor and at least one second field effect transistor, wherein each at least one second field effect transistor is respectively connected in anti-series to the at least one first field effect transistor. Such a circuit is also known as a back-to-back arrangement. This is advantageous in that the semiconductor switching element is suitable for both current directions as a switching element that may have the first and second switching state. Preferably, the semiconductor switching element has a plurality of such transistor pairs, which are connected in parallel. This is advantageous in that the transistors can have a lower maximum current resistance.
In another advantageous embodiment according to the first aspect, the circuit arrangement includes a decoupling circuit module having a galvanic decoupling element, an output, and at least one input. The output is electrically coupled to the semiconductor switching element. The input is electrically coupled to the monitoring circuit and/or to the control device for receiving the first control signal or the second control signal. The galvanic decoupling element galvanically decouples the output and the at least one input, and, in a potential-free manner, connects the output and the at least one input. This is advantageous in that the semiconductor switching element is galvanically isolated from the analog monitoring circuit and/or from the control device.
In a further advantageous embodiment according to the first aspect, the galvanic decoupling element includes an optical transmission element and an optical receiver element. Advantageously, this enables simple and cost-effective production of the decoupling element.
In another advantageous embodiment according to the first aspect, the analog monitoring circuit includes a current sensor and an analog comparator, wherein the analog comparator is designed and arranged so as to generate the first control signal in a manner dependent on a comparison of a predetermined threshold value with a measurement value that is detected by the current sensor and is representative of a current that flows through the energy store. Advantageously, this makes it possible to very precisely and rapidly detect a short-circuit current and/or an overcurrent flowing through the energy store.
The invention features an energy storage system, according to a second aspect. The energy storage system comprises an energy store and a circuit arrangement according to the first aspect. Advantageous embodiments of the first aspect hereby apply also to the second aspect.
The circuit arrangement is preferably designed such that a cumulative time composed of a responsive time of the analog monitoring circuit, plus a switching time of the semiconductor switching element from the first switching state to the second switching state, plus a signal delay time of the first control signal from the output of the analog monitoring circuit to the control terminal, is shorter than a predetermined maximum current rise time and a predetermined inductance of the energy network if the energy network has an ohmic short-circuit. The maximum current rise time is predetermined by a predetermined maximum current that is allowed to flow through the energy store without destroying same.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.
Elements of identical construction or function are provided with the same reference signs throughout the drawings.